This invention relates to ground fault interrupters and particularly ground fault receptacles.
For background and general description, reference is made to Virani et al. U.S. Pat. No. 4,010,431, Mar. 1, 1977, which describes a ground fault receptacle with a switch arrangement on which the present invention improves. A receptacle as described in the patent has in addition to the contacts for opening the hot line and neutral conductors, L and N, respectively, upon the occurrence of a ground fault, a third pair of contacts connected in a circuit branch between the conductors L and N for supplying operating power to the internal electronics of the device. Such a third pair of contacts is very desirable when arranged, as in the patent, to be sequentially operated with the main power contacts so that the third pair of contacts always opens first upon a trip and closes first upon resetting. The sequence of the contacts insures a ground fault will not go undetected upon closing of the power contacts and also insures protection of the internal electronics upon a trip. It is desirable to provide this feature in order to protect against possible damage as may result if the hot line and neutral conductors of the associated electrical distribution system are reversed in their connection to the unit. A primary purpose is to insure complete removal of power from the semiconductor switch of the trip electronics upon an opening so that total line current does not pass therethrough and so it is maintained in the totally off condition regardless of the internal circuitry being of the type in which a capacitance may retain a charge and result in a continual current. By the prior patent the movable armature carrying the movable contacts of the two pairs of main power contacts causes the opening of the contacts to the sensing circuit upon a trip.
The present invention uses the concept of the apparatus of the above patent by having an additional pair of contacts, in addition to the main power contacts, that is the first pair of contacts to open upon a trip of the unit and is the first pair of contacts to close upon a reclosing of the unit in order to insure effective operation as well as to provide protection of the internal electronics. The present invention provides an improvement by having the third pair of contacts arranged in a more simple form than previously so that it is both more economical and more compact than formerly. In addition, the arrangement of the present invention provides more reliable operation of the third pair of contacts as there is insurance against any operation of the power contacts unless the third pair of contacts is closed and the third pair of contacts are more assuredly required to be opened upon a trip before the power contacts.
These multiple objectives and advantages of the present invention are achieved in an arrangement in which the means to supply operating power to the electronic circuit of the unit comprises conductive connections from the line conductors including the latch member which holds the movable member with the power contacts in engagement when it is in its closed position and which releases the power contacts from engagement when it is in its open position. Also, in the specific embodiment to be described hereinafter, the circuit to the electronics includes as a conductive element a spring which provides the closing force on the contact armature plate upon reclosing after a trip. Thus, it is seen that the present invention is one in which the mechanical elements for releasing and moving the power contacts are utilized directly as conductive elements in the circuit for powering the electronics which is both a convenience in terms of simplicity, cost and space saving as well as an enhancement of the reliability of performance of the unit.
While the present invention will be described primarily with reference to a ground fault receptacle, it is not necessarily so limited and it will be seen that its application can be made to ground fault circuit breakers as well.